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Anterior abdominal wall

Last updated: April 9, 2021

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The anterior abdominal wall extends from the xiphoid process and costal margins cranially to the pubic and iliac bones inferiorly and to the mid-axillary lines on either side. The abdomen is divided into regions or quadrants to more precisely describe abdominal symptoms and signs and help identify underlying organs. The muscles of the anterior abdominal wall are flat muscles and include the rectus abdominis, the external and internal obliques, the transversus abdominis, and the pyramidalis. These muscles allow the trunk to bend either forward or laterally, maintain abdominal tone, and help increase intra-abdominal pressure. The main arteries of the anterior abdominal wall are the inferior and superior epigastric arteries. The abdominal wall is innervated by the intercostal nerves, the subcostal nerves, and, to a lesser extent, the iliohypogastric and ilioinguinal nerves.

Boundaries of the anterior abdominal wall

Functions

  • Protects abdominal viscera
  • Assists in forceful expiration
  • Decreases risk of herniation
  • Enables the trunk to bend forward or laterally

Planes of the anterior abdominal wall

Divisions of the abdomen

The regions or quadrants of the abdomen are used in clinical contexts to describe abdominal symptoms and signs and help identify underlying organs.

Regions

  • There are 9 abdominal regions
    • Upper regions: right hypochondriac (1), epigastric (2), left hypochondriac (3)
    • Middle regions: right lumbar (4), umbilical (5), left lumbar (6)
    • Lower regions: right inguinal (7), hypogastric or suprapubic (8), left inguinal (9)
  • They are divided by:

Quadrants

  • There are 4 abdominal quadrants.
    • Upper quadrants: 1. right upper quadrant (RUQ), 2. left upper quadrant (LUQ)
    • Lower quadrants: 3. right lower quadrant (RLQ), 4. left lower quadrant (LLQ)
  • They are divided by horizontal and vertical imaginary lines that intersect at the umbilicus.

Components of the anterior abdominal wall

A defect in the upper linea alba can cause an epigastric hernia.

Herniation of intra-abdominal contents through the linea semilunaris is known as a Spigelian hernia.

Inguinal canal

References:[1][2][3][4]

Overview of the muscles of abdominal wall
Muscle Characteristics Origin Insertion Vascular supply Innervation Function

Anterior muscles

(vertical muscles)

Rectus abdominis
  • Flexes the trunk
  • Maintains abdominal wall tone and helps increase intra-abdominal pressure (e.g., forced expiration, coughing, Valsalva maneuver)
Pyramidalis
  • Small triangular muscle
  • Absent in 10–25% of the population

Anterolateral muscles

(flat muscles)

External oblique

  • Largest abdominal muscle and the most superficial anterolateral muscle
  • Its fibers are oriented in an inferomedial direction (“hand-in-pocket”).
  • Lower 8 ribs (5–12)

Internal oblique

  • Lies deep to the external oblique
  • Its fibers are oriented in a superomedial direction.

Transversus abdominis

  • The deepest muscle of the anterolateral abdominal wall
  • Its fibers are oriented transversely.
  • Maintains abdominal wall tone and helps increase intra-abdominal pressure

The conjoint tendon forms the medial portion of the posterior inguinal canal. A weakness of the conjoint tendon can result in a direct inguinal hernia.

References:[1][2]

Arteries

The inferior epigastric artery forms the lateral boundary for the Hesselbach triangle, which helps distinguish between direct and indirect inguinal hernias intraoperatively.

Veins

Lymphatics

Cutaneous innervation and dermatomes


  1. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016
  2. Chung KW, Chung HM. Gross Anatomy. Lippincott Williams & Wilkins ; 2012
  3. Wyatt M. Oxford Textbook of Fundamentals of Surgery. Oxford University Press ; 2016
  4. Mahadevan V. Anatomy of the anterior abdominal wall and groin. Surgery (Oxford). 2003; 21 (2): p.25-27. doi: 10.1383/surg.21.2.25.14667 . | Open in Read by QxMD
  5. Gray JE, Mizell JS. Anatomy of the Abdominal Wall. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/anatomy-of-the-abdominal-wall.Last updated: September 27, 2017. Accessed: January 3, 2019.